[31.01] A Brief Overview of the Meeting Plan

D. Cox (University of Wisconsin-Madison)

An AAS meeting in Madison provides an excellent opportunity for this special
session on the Diffuse Interstellar Medium. It is a topic on which many here
have worked long and hard, tending to believe that until its intricacies are
sufficienty grasped, one will likely misinterpret much of the behavior of the
post-recombination Universe. In addition, the larger community of those who
work in this arena, both in the US and elsewhere, is active, stimulating, and
decidedly challenging. It is a distinct pleasure to host a general review of
their progress, and the disturbing puzzles that remain.
There have been a variety of conceptions of the interstellar medium; each a
partially successful synthesis of an enormous amount of observational data.
They include ideas about how the gas is distributed, and why; about where it is
ionized, and why; about where very hot gas is located and with what prevalence,
and why; about the roles of cosmic rays and magnetic fields in the overall
structure and activity of the system, and occasionally even some sense of how
things might be different at other galactic radii, or how the whole structure
responds to disturbance by spiral density waves.
This special session focuses primarily on the observational material, but with
specific attention to how the data limit the range of acceptable pictures. It
is also intended to highlight key puzzles, describe anticipated progress from
new instrumentation, and provide a spirited attempt to imagine how things might
actually be out there--and why.